What is male pseudohermaphroditism? Briefly discuss the causes of this condition.

Outline:

·        Definition

·        Causes:

- defective testis

- receptor problem

- defective enzyme pathways

Essay:

            A pseudohermaphrodite is an individual with the genetic constitution and gonads of one sex and the genitalia of the other. Male pseudohermaphroditism describes a syndrome in which a genetically determined male has female external genitalia and notable absence of male genitalia.

            The development of the external genitalia in males begins at 9 to 10 weeks of gestation. Testosterone must be secreted into fetal circulation and then be converted to dihydrotestosterone within the cells of the anlage tissues for the external genitalia to differentiate normally. The presence of the androgen receptor is required in these target tissues. Therefore, any defect along this pathway will lead to abnormal differentiation of male external genitalia and male pseudohermaphroditism.

            A common cause of this condition is a defective embryonic testis which is unable to produce sufficient quantities of testosterone to stimulate external genitalia development. Enzyme defects in the biosynthesis of androgens is another possible cause. Because the testis also secrete antimullerian hormone, genetic males with defective testes have female internal genitalia.

            Another cause is androgen resistance, in which, as a result of various congenital abnormalities, male hormones cannot exert their full effects on the tissues. One form of androgen resistance is 5a-reductase deficiency, in which the enzyme responsible for the formation of dihydrotestosterone is decreased. As a result, no male external genitalia is formed. When the loss of receptor function is complete, the testicular feminization syndrome results. The external genitalia are female, but the vagina ends blindly because there are no female internal genitalia. Individuals with this syndrome develop enlarged breasts at puberty and usually are considered to be normal women until they are diagnosed otherwise.